Method of treating fibrous



Aug. 28, 1934. T. w. BAccHUs R- 19,288

' METHOD OF TREATING FIBROUS MATERIALS Original Filed Sept. 23, 1930Reissuecl Aug 28, 1934 UNITED STATES PATENT OFFICE METHOD OF TREATINGFmRoUs V MA'rERIaLs Thomas W. Bacchus, Wilmington, Del., assignor toHercules Powder Company, -Wilmington, Del., a corporation of Delaware 9Claims. (01. 92-7) My invention relates to a method for treating fibrousmaterials, as for example, cotton linters,

straw, wood, or the like. In the preparation of fibrous materials forvarious purposes, it is desired to efiect removal from the materials ofhull particles or lignous impurities, to efiect saponification of theoils and emulsification of.the waxes, etc., and for certain purposes, asin the preparation of cellulose 10 materialsfifor nitration, it isdesirable to effect reduction in the viscosity of such materials.

Heretofore in the treatment of fibrous materials, it has been generallycustomary to place the materials in large kiers or digesters togetherwith an aqueous caustic soda solution of suitable concentration, or withsulphate liquor, or other purifying solution, and the contents heated,either directly or indirectly, under a pressure between aboutatmospheric and 150 pounds, depending upon the result desired to beobtained. The treatment in the kiers or digesters has heretofore beencontinued for from 1 to 18 hours or more. At the end of the period oftreatement the pressure is released from the kiers or digesters, theliquor drained from the material and the material washed, bleached,dried, etc. as desired.

As an example of the treatment of fibrous materials by methodsheretofore known, dry cotton linters are placed in a kier or digesterwith, for example, a 1%-4% sodium hydroxide .solution in, for example,the ratio of 6 parts of sodium hydroxide solution to 1 part cottonlinters. Steam is applied to the kier or digester at a pressure of, forexample, 60 pounds and maintained for a period of, for example, 5 hours,after which the pressure is released, the liquor drained oil and thetreated linters washed with water,

subjected to treatment with a suitable bleaching agent and finallydried.

The method heretofore used in the treatment of fibrous materials, asabove briefiy outlined, is disadvantageous for many reasons, chief amongwhich are that it involves batch operation, requires large and expensiveapparatus, which in operation, presents various problems of control, isexpensive to maintain, and, at the same time, is capable of only alimited output.

Now, in accordance with my invention, I have 0 discovered that thedesired treatment for the purification of fibrous materials and desiredreduction in viscosity may be eifected in a continuous manner bycontinuously passing the material to be treated in admixture with adesired 5 solution for effecting the treatment, through a zone whereinthe fibrous material is subjected to the action of heat and pressure,the discharge from such a zone being controlled,

In the practical adaptation of the method in accordance with myinvention, for example, the fibrous material, as cotton linters, straw,comminuted wood, or the like, to bepurified, in admixture with apurifying solution may be pumped through a passage, the discharge fromwhich is controlled and in which the mixture of fibrous I material andpurifying solution is subjected to heat at the desired temperature andmaintained under the desired pressure. The temperature will desirably besubstantially above the boiling point of the treating solution, 1. e.substantially above, and preferably will be above about 140 C.

As a more specific illustration of the practical adaptation of myinvention, cotton linters, straw, comminuted wood or the like, may bemixed in a suitable container with a purifying solution, such as asolution of sodium hydroxide, sulphate liquor solution, etc. The mixturemay be pumped from the container through a coil of tubing, the outletfrom which is suitably controlled as, for example,

by providing a suitable' valve, connecting with a 30 standpipe, orotherwise providing for control 01' the outlet.

Having now indicated in a general way the nature and purpose of myinvention, I will more specifically describe a preferred practicaladapta- 35 tion thereof by way of illustration in connection with, forexample, the purification of cotton linters and with reference to theaccompanying drawing by which is illustrated diagrammatically a form ofapparatus adaptable for the carrymg out of the method embodyingmyinvention.

Referring to the drawing, A indicates a container desirably fitted withsome form of agitating device in which the material to be treated may bemixed with a treating solution. B indicates a pump, the suction side ofwhich is connected, with the container A and the discharge side of whichis connected to the inlet end of a coil ofpipe C. A portion of the coilof pipe C adjacent to the discharge of the pump B is jack- 1 eted asshown at d, the jackets being connected and provided with an inlet anddischargefor steam. The coil adjacent its discharge end is jacketed asshown at e, the jackets being connectedand provided with an inlet anddischarge for cooling water. The portion of the coil intermediate thejackets d, e, is covered with insulating material, as for example,asbestos, or the like, as indicated at G.

The discharge or outlet end of the coil C is connected to a valve casingH, within which is provided a valve seat on which is adapted to seat aconoidal shaped valve 1' provided with a stem 1: extending through astufiingbox l .in the casing, and provided at its outer end with a headm against which abuts one end of a spring n, the

- other end of which abuts against an adjustable stop 0 "carried by abracket p attached to the casing. The valve casing H is desirablyconnected to a standpipe Q, which extends upward for a substantialdistance and returns to connection with a surge tank or receiving tank Rfrom which a discharge S is provided. Adjacent the upper portion of thestand pipe Q a vent t, provided with a suitable valve u, is provided. Ifdesired the standpip'e Q may be omitted and the valve casing connecteddirectly to the surge tank R, or the valve ii may be omitted and thecoil C connected directly'to standpipe Q.

Connected to the discharge or outlet end of the coil C, or connected tothe coil adjacent. the dischargeor outlet end, is a pipe V provided witha suitable valve w. Pipe V is connected to the discharge side of a pumpX, the inlet side, through a pipe Y, being connected with a suitablesource of purifying solution or of water.

In carrying out the method in accordance with my invention, in theapparatus'above described, for example, cotton linters are placed in thecontainer A together with an aqueous caustic soda I solution of .5%-,-2% strength, in the-proportion of say 1 part of cotton linters toparts of caustic soda solution by weight. The mixture of cotton lintersand caustic liquor is then pumped bythe pump B through the coil C at. avelocity of say 'about 2 feet per second. The mixture of cotton lintersand caustic solution are brought to a suitits up 'standpipe Q and downinto tank 1%. The] standplpe Q may be made of any desired height,

able temperature, say about 165 C. by the introduction of steam into thejackets d or, if desired, live steam may be injected into the coil at asuitable point or points to obtain the desired temperature.- Thetemperature ofthe'mixture of cotton linters and caustic solution ismaintained at approximatlylfifi" C. in its travel through that part ofthe coil whlch is insulated,

and is suitably reduced toa point below the boiling point of the causticsolution before discharge from the coil through the introduction ofcooling water into the jackets e. -The mixture is desirably maintainedunder a pressure of about 200 lbs. per square inch in its passagethrough the coil, by adjustment of valve 1. P

In the treatment of cotton linters as indicated above, the section ofthe coilprovided with steam jackets d may be of any suitable length toobtain the desiredtemperature and the portion of coil provided withcooling jackets 2 may be of any lieve any jani. Thus, the valve willtend to unitormly control discharge from, and hence equalize thepressure on the coil C. The mixture of cotton linters and causticsolution discharged from the' coil 0 will, after passing-through thevalve, pass its purpose being primarily tocooperate with the valve i incontrolling the discharge from and through the valve i.

is passed through the zoneoi' treatment or coil equalize the pressure onthe coil C. Under certain circumstances the control of the dischargefrom the coil 0 may be eflected by connecting the discharge directlywith the standpipe Q, the valvei being omitted. In such case thestandpipe Q would be made of sufllcient height' so that desired controlof the discharge from the coil would be eiiected through the pressure ofthe column of cotton linters and solution in the standpipe. It will benoted thatthe standpipe is provided with a vent controlled by a suitablevalve in order to prevent or control the creation of a vacuum by thedownwardly passing cotton linters and solution upon the columncommunicating with the coil. .7

, During the passage of cotton linters and solution through the coil Cspent caustic soda solution or water is desirably pumped by pump Kthrough the pipe V and passes with the cotton linters and solutiondischarged from the coil through the valve 1'. The spent caustic sodasolution or water supplied by pump X acts to increase the ratio ofcaustic soda solution to cotton over that of the mixture discharged fromthe coil with the result that the mixture will more readily pass Thecotton linters. discharged into tank B. may be drawn therefrom asdesired for separation from the purifying solution, ashing andsubjecting to such other treatme t as may be desired.

The productwithdrawn from tank R, as for example, cotton linters, straw,comminuted wood, or the like, which may have been treated, will be foundto have great purity, to be free from waxes, 1

oils and from hulls and encrusting materials and to be of a desiredreduced viscosity. The product will be obtained with great reduction oftime,

labor, and with very simple apparatus.

It will be appreciated that in the carrying out 113 of my invention theprecise temperature and pressure used and the time or treatment willdepend upon the material treated and the desired characteristics ofpurity, reduced viscosity, soft ness, etc. desired. It will beappreciated that the time oi? treatment may be readily varied for thetreatment of any particular material and for the production of anyparticular grade of product by a regulation of the velocity at which thematerial and the extent of the zone or coil.

It will be appreciated that the method in accordance with my inventionis not dependent upon, the use of any particular form of apparatus andthat-that described herein is disclosed merely forpurposes ofillustration. It will be further appreciated that in carrying out themethod in accordance with my invention various modifications may be madewithout departingfrom my inven 135 tion. I

"What I claim and desire protect by Patent is:.-

1. The method of treating fibrous material which includes forcing amixture of fibrous ma- 14o terial and a treating solution under pressurethrough a passage, heating the mixture adjacent the'inletend of saidpassage, cooling the mixture adjacent the discharge end of saidpassage'and controlling thedischargejrom said passage.

2; The method of treating cotton linters which includes forcing amixture of cotton linters and a caustic soda solution under,pressurethrough apassage, heating the mixture at a point within saidpassage, cooling the adjacent the 56 discharge end of said passage andcontrolling the discharge from said passage.

3. The method of treating fibrous cellulosic material which includesforcing a mixture of fibrous cellulosic material and an alkalinetreating solution through a passage, heating the mixture within thepassage to a temperature substantially above the boiling point of thetreating solution at atmospheric pressure, cooling the mixture adjacentthe discharge end of said passage to a temperature below theboilingpoint of the treating solution and controlling the discharge fromsaid passage.

4. The method of treating fibrous cellulosic material which includesforcing a mixture of fibrous cellulosic material and an alkalinetreating solution comprising an aqueous solution of caustic soda,through a passage, heating the mixture within the passage to atemperature higher than about 140 C., cooling the mixture adjacent thedischarge end of said passage to a temperature below the boiling pointat atmospheric pressure of the treating solution and controlling the,discharge from said passage.

5. The method of treating cotton linters which includes forcing amixture of cotton lintersand a treating solution comprising an aqueoussolution of caustic soda, through a passage, heating the mixture withinthe passage to a temperature substantially abovethe boiling point of thetreating solution at atmospheric pressure, cooling the mixture adjacentthe discharge end of said passage to' a temperature below the boilingpoint of the treating solution and controlling the discharge from saidpassage.

6. The method of treating cotton linters which includes forcing amixture of cotton linters and a treating solution comprising an aqueoussolution containing about 0.5-2% sodium hydroxide by weight, through apassage, heating the mixture within the passage to a temperaturesubstantially above the boiling point of the treating solution atatmospheric pressure, cooling the mixture adjacent the discharge end ofsaid passage to a temperature below the boiling point of the treatingsolution and controlling the discharge from said passage.

' 7. The method of treating fibrous cellulosic material which includesforcing a mixture of fibrous cellulosic material and a treating solutioncomprising an aqueous solution containing about 0.5-2% sodium hydroxideby weight through a passage, heating the mixture within the passage to atemperature of about 165 C., cooling the mixture adjacentthe dischargeend of said passage to a temperature below the boiling point of thetreating solution at atmospheric pressure and controlling the dischargefrom the passage. 8. The method of treating fibrous cellulosic .materialwhich includes forcing a mixture of fibrous cellulosic material and atreating solution through a passage, introducing steam into the passageto heat the mixture to a temperature substantially above the boilingpoint of the treating solution, cooling the mixture adjacent to thedischarge end of the passage to a temperature below the boiling point ofthe treating solution at atmospheric pressure and controlling thedischarge from the passage.

9. The method of treating cotton linters which includes forcing amixture of cotton linters and a treating solution comprising an aqueoussolution containing about 0.5-2 by weight of sodium hydroxide through apassage, introducing steam into the passage to eifect heating of themixture to a temperature higher than about 140 C., cooling the mixtureadjacent the discharge end of the passage to a temperature below theboiling point of the treating solution at atmospheric pressure andcontrolling the discharge from the passage.

THOMAS W. BACCHUS.

